"You are a very good person."
Translation:Sen çok iyi bir insansın.
They are usually exchangeable but there are some differences.
İnsan sounds more empathetic than kişi. İnsan has more focus on being human and kişi has more focus on individuality.
Kişi is often used when you count people or when you group people and label them.
İnsan also means human. Kişi does not mean human.
Kişi must have an adjective or a relative clause that describes it. It cannot be used on its own. (There may be some exceptions in the formal language) e.g. People are coming. - İnsanlar geliyor. (not Kişiler geliyor.)